U.S. patent application number 17/006340 was filed with the patent office on 2021-03-04 for method for validating voltage measurements in a digital-electricity transmission system.
This patent application is currently assigned to VoltServer, Inc.. The applicant listed for this patent is VoltServer, Inc.. Invention is credited to Stephen S. Eaves.
Application Number | 20210063447 17/006340 |
Document ID | / |
Family ID | 74681673 |
Filed Date | 2021-03-04 |
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United States Patent
Application |
20210063447 |
Kind Code |
A1 |
Eaves; Stephen S. |
March 4, 2021 |
Method for Validating Voltage Measurements in a Digital-Electricity
Transmission System
Abstract
Transmission-line voltage measurements in a digital-electricity
power system are validated by acquiring a series of
transmission-line voltage measurements during a sample period when
a transmitter-disconnect device is in a non-conducting state. A
numerical analysis is performed to determine a point in time at
which AC components in the transmission line have diminished and at
which the primary change in the transmission-line voltage
measurement values is due to DC decay. A receiver acquires a series
of receiver-voltage measurements during the same sample period; and
a numerical analysis is performed on the receiver-voltage
measurements to determine the point in time at which the AC
components have diminished and where the primary change in the
transmission-line voltage measurement values is due to DC decay.
The transmitter-disconnect device is then placed in a
non-conducting state based on an evaluation of those
measurements.
Inventors: |
Eaves; Stephen S.;
(Charlestown, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
VoltServer, Inc. |
East Greenwich |
RI |
US |
|
|
Assignee: |
VoltServer, Inc.
East Greenwich
RI
|
Family ID: |
74681673 |
Appl. No.: |
17/006340 |
Filed: |
August 28, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62893281 |
Aug 29, 2019 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01R 19/16528 20130101;
H02H 3/00 20130101; G01R 19/2509 20130101; G01R 19/2513
20130101 |
International
Class: |
G01R 19/165 20060101
G01R019/165; G01R 19/25 20060101 G01R019/25 |
Claims
1. In a digital-electricity power system comprising at least one
transmitter, each transmitter monitoring and controlling voltage on
respective transmission lines and interacting with one or more
receivers connected to an opposite end of the respective
transmission lines, a method for validating transmission-line
voltage measurements, comprising: a) acquiring a series of
transmission-line voltage measurements during a sample period when
a transmitter-disconnect device is in a non-conducting state; b)
performing numerical analysis on the transmission-line voltage
measurements to determine a point in time at which AC components in
the transmission line have diminished and at which the primary
change in the transmission-line voltage measurement values is due
to DC decay, and storing a first voltage measurement acquired at
that point in time; c) using the receiver to acquire a series of
receiver voltage measurements during the same sample period; d)
performing numerical analysis on the receiver voltage measurements
to determine the point in time at which the AC components have
diminished and at which the primary change in the transmission-line
voltage measurement values is due to DC decay and storing a second
voltage measurement acquired at that point in time; e) storing a
difference calculation resulting from subtracting the first stored
voltage measurement from the second stored voltage measurement; and
f) placing the transmitter-disconnect device in a non-conducting
state if the absolute value of the difference calculation is
greater than a predetermined maximum value, wherein the
transmission-line voltage measurements cannot be validated.
2. The method of claim 1, wherein the transmitter acquires the
series of transmission-line voltage measurements, stores the
difference calculation, and takes action to place the
transmitter-disconnect device in the non-conducting state, and
wherein the transmitter or the receiver is used to perform the
numerical analysis on the transmission-line voltage.
3. The method of claim 1, wherein the receiver performs the
numerical analysis on the receiver voltage measurements, produces
the transmission-line voltage measurement values, and communicates
the transmission-line voltage measurement values to the
transmitter.
4. The method of claim 1, wherein the receiver voltage measurements
acquired by the receiver are communicated to the transmitter
without performing the numerical analysis that determines when the
AC components have diminished, and where the numerical analysis of
the receiver voltage measurements is performed by the
transmitter.
5. The method of claim 1, wherein, when the transmitter determines
that the AC components of the transmission-line voltage
measurements do not diminish within a predetermined time period,
then the transmitter takes action to place the
transmitter-disconnect device in a non-conducting state and
registers a fault because the transmission-line voltage is
considered unstable.
6. The method of claim 1, wherein the transmitter and receiver
first determine a point in time when the AC components of their
respective voltage measurements have diminished and then average a
plurality of transmission-line voltage measurements after that
point to produce one average voltage value for the transmitter and
one average voltage value for the receiver, and wherein the
transmitter uses the difference in the average values to determine
if the transmission-line voltage measurements are valid.
7. The method of claim 1, wherein the transmitter is in electrical
communication with a voltage source, the method further comprising
the transmitter varying the voltage of the voltage source to
perform voltage measurements over a wider range and testing whether
voltage measurements by the receiver and voltage measurements by
the transmitter continue to match when the primary change in the
transmission-line voltage measurements is due to DC decay at
different voltages.
8. The method of claim 1, wherein the receiver is supplied with the
transmission-line voltage measurements, performs the difference
calculations and communicates back to the transmitter if the
transmission-line voltage measurements are invalid, and wherein the
transmitter takes action to place the transmitter-disconnect device
in a non-conducting state.
9. A digital-electricity power system, comprising: at least a pair
of transmission lines; at least one transmitter in electrical
communication with a transmission end of the transmission lines,
wherein the transmitter is configured to transmit
digital-electricity power over the transmission lines and is
further configured to monitor and control voltage on respective
transmission lines; and at least one receiver in electrical
communication with a receiving end of the transmission lines,
wherein the transmitter is configured to interact with the
receiver; a controller in the transmitter or in the receiver,
wherein the controller includes a processor and a computer-readable
medium in communication with the process and non-transitorially
storing software code including instructions for: a) using the at
least one transmitter to acquire a series of transmission-line
voltage measurements during a sample period when a
transmitter-disconnect device is in a non-conducting state; b)
using the receiver to acquire a series of receiver voltage
measurements during the same sample period; c) transferring the
receiver voltage measurements to the transmitter; d) calculating
when AC components of the transmission-line voltage measurements
and AC components of the receiver voltage measurements have
diminished to a point at which the primary change in the
transmission-line voltage measurements is due to DC decay and
storing a first voltage measurement acquired at that point; e)
determining the voltage values at the transmitter and receiver at a
point after the AC components have diminished to the point at which
the primary change in the voltage measurements is due to DC decay
in both the transmission-line and receiver voltage measurements;
and f) placing the transmitter-disconnect device in a
non-conducting state if the difference between the values is
greater than a predetermined maximum value, wherein the
transmission-line voltage measurements cannot be validated.
10. The digital-electricity power system of claim 9, wherein the
receiver is supplied with the transmitter voltage measurements,
performs the difference calculations and communicates back to the
transmitter if the transmission-line voltage measurements are
invalid, wherein the transmitter takes action to place the
transmitter-disconnect device in a non-conducting state.
11. The digital-electricity power system of claim 9, wherein the
receiver voltage measurements acquired by the receiver are first
processed by the receiver to determine the point where the AC
components have substantially diminished, and communicates back to
the transmitter a value representative of the voltage at the
receiver end of the transmission lines after the AC components have
diminished.
12. The digital-electricity power system of claim 9, wherein, when
the transmitter determines that the AC components of the
transmission-line voltage measurements do not diminish within a
predetermined time period, then the transmitter takes action to
place the transmitter-disconnect device in a non-conducting state
and registers a fault because the transmission-line voltage is
considered unstable.
13. The digital-electricity power system of claim 9, wherein the
transmitter and receiver first determine a point in time when the
AC components of their respective voltage measurements have
diminished and then average a plurality of transmission-line
voltage measurements after that point to produce one average
voltage value for the transmitter and one average voltage value for
the receiver, and where the transmitter uses the difference in the
average values to determine if the transmission-line voltage
measurements are valid.
14. The digital-electricity power system of claim 9, wherein the
transmitter is in electrical communication with a voltage source,
the method further comprising the transmitter varying the voltage
of the voltage source to perform voltage measurements over a wider
range and testing whether voltage measurements by the receiver and
voltage measurements by the transmitter continue to match during
the DC decay period at different voltages.
Description
RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional
Application No. 62/893,281, filed 29 Aug. 2019, the entire content
of which is incorporated herein by reference.
FIELD OF INVENTION
[0002] This invention relates to power-distribution-system
safety-protection devices--for example, power-distribution systems
with electronic monitoring to detect and disconnect power in the
event of an electrical fault or safety hazard, particularly where
the power transmission lines are dissipating an abnormally high
amount of power loss--often called a "resistive fault" or "in-line
fault". More specifically, this invention can be used in
digital-electricity transmission systems. This invention is
applicable to general power distribution and, in exemplifications,
to, e.g., electric vehicle charging, telecommunications or
alternative energy power systems.
BACKGROUND
[0003] Digital electric power, or digital electricity, can be
characterized as any power format where electrical power is
distributed in discrete, controllable units of energy. Packet
energy transfer (PET) is a new type of digital electric power
protocol disclosed in U.S. Pat. Nos. 8,068,937, 8,781,637 (Eaves
2012), and international patent application PCT/US2017/016870,
filed 7 Feb. 2017.
[0004] The primary discerning factor in a digital-power
transmission system compared to traditional analog power systems is
that the electrical energy is separated into discrete units; and
individual units of energy can be associated with analog and/or
digital information that can be used for the purposes of optimizing
safety, efficiency, resiliency, control, or routing. Since the
energy in a PET system is transferred as discrete quantities, or
quanta, it can be referred to as "digital power" or "digital
electricity".
[0005] As described in Eaves 2012, a source controller and a load
controller are connected by power-transmission lines. The source
controller of Eaves 2012 periodically isolates (disconnects) the
power transmission lines from the power source and analyzes, at a
minimum, the voltage characteristics present at the
source-controller terminals directly before and after the lines are
isolated. The time period when the power lines are isolated was
referred to by Eaves 2012 as the "sample period", and the time
period when the source is connected is referred to as the "transfer
period". The rate of rise and decay of the voltage on the lines
before, during and after the sample period reveal if a fault
condition is present on the power transmission lines. Measurable
faults include, but are not limited to, short circuits, high line
resistance, or the presence of an individual who has improperly
come in contact with the transmission lines.
[0006] Eaves 2012 also describes digital information that may be
sent between the source and load controllers over the power
transmission lines to further enhance safety or provide general
characteristics of the energy transfer, such as total energy or the
voltage at the load controller terminals. One method for
communications on the same digital-power transmission lines as used
for power was further described and refined in US Pat. No.
9,184,795 (Eaves Communication Patent).
[0007] U.S. Pub. Pat Application No. 2016/0134331 A1 (Eaves Power
Elements) describes the packaging of the source-side components of
Eaves 2012, in various configurations, into a device referred to as
a digital-power transmitter.
[0008] U.S. Pat. No. 9,419,436 (Eaves Receiver Patent) describes
the packaging of various configurations of the load-side components
of Eaves 2012 into a device referred to as a digital-power
receiver.
[0009] U.S. Pub. Pat Application No. 2018/0313886 A1 (Mlyniec Line
Integrity) describes methods for verifying that voltage
measurements on the transmitter side of the system meet minimum
requirements for integrity in an environment containing electrical
noise and where certain transmission-line properties are
unknown.
[0010] The methods described in this specification build on the
earlier work of Eaves 2012 and Mlyniec Line Integrity by focusing
on a novel method to ensure the accurate detection of what was
described in Eaves 2012 as an "in-line" fault. The electrical
industry often uses the term, "resistive fault", interchangeably
with "in-line" fault. In-line faults are defined as a fault where
excessive power losses are experienced in the transmission lines
between the source and load devices. For example, a loose
termination can result in a high connection resistance. The high
resistance can result in heating that can in-turn result in fire.
In-line faults are one of the primary causes of electrical fires in
the power distribution industry.
[0011] Eaves 2012, column 3, described a method for comparing the
transmission line voltage on the transmitter side with the
transmission line voltage as measured by the receiver in the
receiver side of the transmission line. The difference in voltage
combined with a known value of electrical current can be used to
determine the in-line power loss value.
[0012] However, practical considerations for sensor accuracy,
electrical noise and wiring errors make it advantageous to derive a
method for validating the receiver-voltage measurements. This
specification provides a method for the transmitter to obtain a
valid measurement of the transmission-line voltage, as sampled by
the receiver, and for validating the measurement without
interrupting the normal transfer of electrical energy under
packet-energy-transfer (PET) protocol.
SUMMARY
[0013] A method for obtaining a measurement of the
transmission-line voltage from the receiver and for verifying the
integrity of the measurement is described herein, where various
embodiments of the methods and apparatus for performing the method
may include some or all of the elements, features and steps
described below.
[0014] In a digital-electricity power system comprising at least
one transmitter, each transmitter monitors and controls voltage on
a respective transmission line and interacts with one or more
receivers connected to an opposite end of the respective
transmission line, transmission-line voltage measurements are
validated by acquiring a series of transmission-line voltage
measurements during a sample period when a transmitter-disconnect
device is in a non-conducting state. Numerical analysis is
performed on the transmitter-voltage measurements to determine a
point in time at which AC components in the transmission line have
diminished and at which the primary change in the transmission-line
voltage measurement values is due to DC decay and stores a first
voltage measurement acquired at that point in time. The receiver is
used to acquire a series of receiver-voltage measurements during
the same sample period; and numerical analysis is performed on the
receiver-voltage measurements to determine the point in time at
which the AC components have diminished and at which the primary
change in the transmission-line voltage measurement values is due
to DC decay and storing a second voltage measurement acquired at
that point in time. A difference calculation resulting from
subtracting the first stored voltage measurement from the second
stored voltage measurement is stored; and the
transmitter-disconnect device is placed in a non-conducting state
if the absolute value of the difference calculation is greater than
a predetermined maximum value, wherein the transmission-line
voltage measurements cannot be validated.
[0015] The detection of line faults involves periodic measurement
of transmission line voltage. As will be described in detail, as
line currents exceed 2-3 Amps on long transmission lines, detecting
a fault representing excessive power loss on the transmission line
becomes more difficult. This fault is referred to as an in-line
fault. The difficulty can be alleviated by obtaining a signal
representative of the voltage of the transmission line, measured on
the receiver side of the transmission line. It is advantageous to
have the ability to validate the measurement of the receiver-side
voltage for accuracy without de-energizing the load. The disclosed
method can be used to measure and ensure the integrity of the
signal thus preventing false positive or false negative in-line
fault determinations.
[0016] In executing PET protocol inherent to digital electricity,
as described in Eaves 2012, a portion of the total energy packet
period is allocated for the transfer of energy from the source to
the load. This portion is referred to as the transfer period. The
remaining time in the packet period is allocated for detecting
faults and transferring data. This portion of the packet is
referred to as the sample period.
[0017] In a first embodiment of in-line power loss determination
described in Eaves 2012, Column 4, Lines 1-15, the transmitter
samples the transmission line voltage obtained on the transmitter
side of the transmission line during the transfer period when
electrical current is allowed to flow in the line. A second
measurement is taken by the transmitter during the sample period
when no electrical current is flowing. The difference between the
two voltage samples represents the voltage drop on the line between
the transmitter and receiver. Multiplying the voltage drop by an
electrical-current measurement performed by the transmitter
produces a value representative of the in-line power loss on the
transmission lines. If the loss exceeds a predetermined maximum, an
in-line power fault is registered, and the transmitter de-energizes
the line to avoid a fire or burn hazard.
[0018] In a second embodiment of in-line power-loss determination
described in Eaves 2012, Column 3, Lines 50-65, the transmitter
acquires a measurement of the transmission-line voltage at the
transmitter terminals during the transfer period, and receives a
second measurement, via an external communications link, of the
transmission-line voltage, as acquired by the receiver during the
transfer period, at the receiver terminals. The difference between
the two samples represents the voltage drop on the line between the
transmitter and receiver. Multiplying the voltage drop by an
electrical-current measurement performed by the transmitter
produces a value representative of the in-line power loss on the
transmission lines.
[0019] In the first embodiment, described above, it becomes
difficult to measure voltage accurately during the sample period
because of line reflections and electrical noise from external
electro-magnetic sources and adjacent digital-electricity
transmission lines. The difficulty increases with higher currents
and power levels. Line reflections are more pronounced in
transmission lines with lengths exceeding two kilometers. In
practice, in these long transmission lines, electrical currents
above three or four amperes present significant challenges for
accurate calculation of in-line power loss where an accuracy within
+/-10 Watts is desirable. These problems and some solutions are
presented in detail in U.S. Pub. Pat Application No. 2018/0313886
A1 (Mlyniec Line Integrity).
[0020] The second embodiment avoids much of the trouble of the
first embodiment by using transmitter-side and receiver-side
measurements that occur during the transfer period and before the
transmission line current is interrupted in the sample period. The
interruption of the transmission line current is a primary cause of
line reflections. Additionally, measurements during the transfer
period are inherently less susceptible to electrical-noise sources
because the transmission-line impedance is much lower (because the
line is not electrically isolated by the source- and
load-disconnect devices), meaning that much more energy to is
required to impose noise upon it.
[0021] However, a shortcoming of the second embodiment, not
anticipated by Eaves 2012, can be improper validation of the
receiver-side voltage measurement. For example, the receiver-side
voltage-measurement circuitry can become uncalibrated, or a
receiver with a different analog or digital gain factor can be
inadvertently installed.
[0022] One less-desirable solution to this shortcoming can be to
implement a self-test using a predetermined, calibrated, test
voltage. Such a test, however, would need to be performed when the
line is not transferring power, because any current in the
transmission lines will cause a resistive voltage drop and,
therefore, measurement error. Performing the test prior to initial
power-up can also be impractical because the lines may afterwards
operate for years without another opportunity to re-test and the
test information may soon become "stale" and invalid. Periodically
de-energizing the transmission lines to perform the test is
impractical because the power provided is often critical to the
operation of customer equipment.
[0023] A second less-desirable solution to the short-coming is to
perform a test that compares the transmitter-side and receiver-side
voltages during the transfer period, when current is flowing, and
factor out the line-voltage drop due to current flow using
software/firmware algorithmic methods. This approach, however, can
also be impractical because the resistance and length of the
transmission lines must be considered unknown to account for
installation errors; and any operator input that might define it
would be subject to human error.
[0024] The advantageous solution of this specification is to
perform a calibration test during the sample period, rather than
during the transfer period, and to then use the calibration to
validate the transmission-line voltage measurements that are made
during the transfer period. In other words, the second embodiment
proposed by Eaves 2012 for measuring transmission-line voltages
during the transfer period can be combined with a calibration or
validation of the voltage-measurement capability during the sample
period.
[0025] When performing the calibration test during the sample
period, the transmitter has interrupted current to the transmission
lines. During the test, both the receiver and transmitter measure
the transmission-line voltage. The receiver communicates the
voltage to the transmitter, using either the external communication
link proposed in Eaves 2012 or the in-line communications method
disclosed in U.S. Pat. No. 9,184,795 (Eaves Communication Patent).
The transmitter verifies that the receiver voltage matches its own
transmitter-side measurement.
[0026] Although the approach appears simple in theory, in practice
it can be hindered by line reflections and electro-magnetic
interference. Line reflections emanate from the disruption in
current when the transmitter-disconnect device interrupts current
in transmission lines. The line reflections and interference can
appear as voltage peaks that "bounce" between the transmitter and
receiver.
[0027] The technique exploits a novel principle for a digital
electricity system to validate the receiver-voltage
measurement.
[0028] During the sample period, when all alternating-current (AC)
components have diminished, as determined by the transmitter,
despite the fact that the line voltage may still be decaying on a
direct-current (DC) level from factors, such as cross-line
resistance or even a cross-line fault, the voltage at the
transmitter terminals and the voltage at the receiver terminals
should be equal, even when separated by a long distance. Any
non-equality is indicative of hardware failure or
miscalibration.
[0029] As is described in Eaves 2012, both the transmitter and
receiver components include disconnect devices that isolate the
transmission lines from the energy source and the load during the
sample period (the disconnect devices are referred to in Eaves 2012
as the source disconnect and load disconnect). Any AC component on
the transmission lines during the sample period is then a
combination of either line reflections or electrical noise being
induced onto the lines. By first determining when the AC components
have diminished to an insignificant level, and then separating them
from subsequent voltage samples that represent only DC decay on the
transmission lines, a valid voltage calibration point can be
obtained. If the AC components do not diminish during the sample
period, then the system is considered unstable; and the transmitter
will initiate a fault shut-down by opening its disconnect
device.
[0030] The safety functions of a digital electricity system involve
a) transmission-line voltage measurements made sequentially that
are compared differentially, or, in the case of in-line faults, b)
a differential comparison of the transmitter terminal voltage
measurements, as made by the transmitter to receiver terminal
voltage measurements. By having the ability to validate voltage
measurements made by the transmitter and receiver, a resilient
method to ensure accurate in-line fault measurements is
obtained.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] FIG. 1 is a block diagram of an exemplification of the safe
power distribution system.
[0032] FIG. 2 is an illustration of a packet-energy-transfer
voltage waveform.
[0033] FIG. 3 illustrates in-line power loss determination for a
transmission line in the absence of electrical noise or line
reflections.
[0034] FIG. 4 illustrates an in-line power loss determination for a
long transmission line with line reflections.
DETAILED DESCRIPTION
[0035] The foregoing and other features and advantages of various
aspects of the invention(s) will be apparent from the following,
more-particular description of various concepts and specific
embodiments within the broader bounds of the invention(s). Various
aspects of the subject matter introduced above and discussed in
greater detail below may be implemented in any of numerous ways, as
the subject matter is not limited to any particular manner of
implementation. Examples of specific implementations and
applications are provided primarily for illustrative purposes.
[0036] Unless otherwise defined, used or characterized herein,
terms that are used herein (including technical and scientific
terms) are to be interpreted as having a meaning that is consistent
with their accepted meaning in the context of the relevant art and
are not to be interpreted in an idealized or overly formal sense
unless expressly so defined herein.
[0037] The terminology used herein is for the purpose of describing
particular embodiments and is not intended to be limiting of
exemplary embodiments. As used herein, singular forms, such as "a"
and "an," are intended to include the plural forms as well, unless
the context indicates otherwise. Additionally, the terms,
"includes," "including," "comprises" and "comprising," specify the
presence of the stated elements or steps but do not preclude the
presence or addition of one or more other elements or steps.
[0038] A representative digital-power system, as originally
described in Eaves 2012, is shown in FIG. 1. The system includes a
voltage source 1 and at least one load 2. The PET protocol is
initiated by an operating switch 3 to periodically disconnect the
source 1 from the power transmission lines 22 electrically joining
the source 1 with the load 2. When the switch 3 is in an open
(non-conducting) state, the lines are also isolated by isolation
diode (D.sub.1) 4 from any stored energy that may reside at the
load 2.
[0039] Eaves 2012 offered several versions of alternative switches
that can replace the isolation diode 4, and all versions can
produce similar results when used in the presently described
methods. Capacitor C.sub.3 5 is representative of an energy-storage
element on the load side of the circuit.
[0040] The transmission lines 22 have inherent line-to-line
resistance R.sub.4 6 and capacitance C.sub.1 7. The PET system
architecture, as described by Eaves 2012, adds additional
line-to-line resistance R.sub.3 8 and capacitance C.sub.2 9. At the
instant switch 3 is opened, capacitances C.sub.1 7 and C.sub.2 9
have stored charge that decays at a rate that is inversely
proportional to the additive values of resistances R.sub.4 6 and
R.sub.3 8. Capacitor C.sub.3 5 does not discharge through
resistances R.sub.3 8 and R.sub.4 6 due to the reverse blocking
action of isolation diode D.sub.1 4. The amount of charge contained
in capacitors C.sub.1 7 and C.sub.2 9 is proportional to the
voltage across them and can be measured at points 16 and 17 by a
source controller 18 or load controller 19.
[0041] As described in Eaves 2012, a change in the rate of decay of
the energy stored in capacitances C.sub.1 7 and C.sub.2 9 can
indicate that there is a cross-line fault on the transmission lines
22. The difference between normal operation and a fault, as
presented by Eaves 2012, is illustrated in FIG. 2.
[0042] Referring again to FIG. 1, the combination of switch S.sub.1
3; source controller 18; resistor R.sub.1 10; switch S.sub.2 11;
and resistor R.sub.3 8 can be referred to as a transmitter 20. The
combination of switch S.sub.4 15; resistor R.sub.5 14; load
controller 19; diode D.sub.1 4; capacitor C.sub.2 9; and capacitor
C.sub.3 5 can be referred to as a receiver 21.
[0043] A method to measure in-line resistance without a
communications link, as specified in Eaves 2012, is depicted in
FIG. 3, which shows an ideal case where there are no line
reflections or external electrical noise. The transmitter 20
measures its terminal voltage and electrical current nearly
simultaneously in a first sample 23 during the same energy-transfer
period just before opening the source disconnect S.sub.1 3. The
transmitter 20 opens disconnect switch S.sub.1 3 and immediately
takes another voltage sample 25. The difference between the first
and second voltage samples 23 and 25 is proportional to the line
resistance. The voltage difference between the first and second
voltage samples 23 and 25 is independent of the normal, slower
decay in voltage that occurs for the remainder of the sample period
because the second voltage sample 25 is taken before the voltage on
the transmission lines 22 has had time to decay significantly. By
multiplying the difference in voltage by the current measurement, a
value of in-line power loss is obtained.
[0044] FIG. 4 depicts the transmission-line voltage as seen by the
transmitter 20 (solid line) and as seen by the receiver 21 (dashed
line) in a longer transmission line and/or at higher electrical
currents. In this case, line reflections increase the complexity of
making the simple in-line power-loss calculation described for FIG.
3. At the point where the transmitter-disconnect switch S.sub.1 3
is opened 24, the line voltage is higher at the transmitter
terminals 24 than it is at the receiver terminals 26 due to the
voltage drop when current is passed through the resistance of the
transmission line 22. As can be seen by the difference in the
horizontal axis positions of points 24 and 26 in FIG. 3
(representing the voltage at the transmitter and receiver
terminals, respectively), there is also a time delay, due to the
inductive and capacitive elements of the line 22, from when the
transmitter disconnect first causes a drop in voltage as seen at
the transmitter terminals 24, and when the drop is first seen at
the receiver terminals 26. Using numerical-processing techniques
well known in the signal-processing industry, the transmitter
processor and receiver processor can make a determination of when
the AC components of the transmission-line voltage have diminished
to an insignificant value, at point 28, and where the remaining
change in voltage is a DC decay due to the cross-line resistance of
the transmission lines 22 or a cross-line fault, both of which are
forms of DC decay. Further refinements on separating DC decay from
AC components were described in the Mlyniec Line Integrity Patent,
but Mlyniec did not disclose the ability to validate receiver-side
measurements. At point 30, the transmitter closes the disconnect
switch S.sub.1 3 again, and the voltage of the transmission line 22
rises.
[0045] It is in the area between points 28 and 30 that the voltage,
as measured at the transmitter terminals 24, and the voltage, as
measured by the receiver terminals 26, should match. Both the
transmitter 20 and receiver 21 then calculate an average voltage
value for the period between points 28 and 30. The receiver 21
transmits the average voltage value that it measured to the
transmitter 20 using the communications link described in Eaves
2012 or using a communications data stream imposed on the
transmission lines 22, as described in the Eaves Communication
patent.
[0046] In some cases, it would be useful for the transmitter 21 to
vary the value of its voltage source for the purposes of performing
voltage measurements over a wider range and, therefore, testing
whether the voltage measurements by the receiver 21 and voltage
measurements by the transmitter 20 continue to match during the DC
decay period. This technique can uncover problems related to gain
error in the analog or digital calibration of the voltage sensing
components. Alternatively, via the transmitter 20 changing its
source voltage according to a predetermined pattern, the technique
can be used to verify that the transmitter 20 is communicating with
the correct receiver 21, particularly when an external
communication link is used, as the communication connection could
be inadvertently connected between the wrong transmitter
20/receiver 21 pair.
[0047] There are a number of numerical techniques well known to the
signal-processing industry to extract the average voltage value
between point 28 and point 30 of FIG. 3. These techniques can
include simple averaging, digital filtering or interpolation
methods, some of which are described in the Mlyniec Line Integrity
Patent. Signal-processing tasks otherwise performed by the receiver
21 can be off-loaded to the transmitter 20 by transmitting "raw"
voltage measurements from the receiver 21 to the transmitter
20.
[0048] The systems and methods of this disclosure can be
implemented in a computing-system environment. Examples of
well-known computing system environments and components thereof
that may be suitable for use with the systems and methods include,
but are not limited to, personal computers, server computers,
hand-held or laptop devices, tablet devices, smart phones,
multiprocessor systems, microprocessor-based systems, set-top
boxes, programmable consumer electronics, network personal
computers (PCs), minicomputers, mainframe computers, distributed
computing environments that include any of the above systems or
devices, and the like. Typical computing system environments and
their operations and components are described in many existing
patents (e.g., U.S. Pat. No. 7,191,467, owned by Microsoft
Corp.).
[0049] The methods may be carried out via non-transitory
computer-executable instructions, such as program modules.
Generally, program modules include routines, programs, objects,
components, data structures, and so forth, that perform particular
tasks or implement particular types of data. The methods may also
be practiced in distributed computing environments where tasks are
performed by remote processing devices that are linked through a
communications network. In a distributed computing environment,
program modules may be located in both local and remote computer
storage media including memory storage devices.
[0050] The processes and functions described herein can be
non-transitorially stored in the form of software instructions in
the computer. Components of the computer may include, but are not
limited to, a computer processor, a computer storage medium serving
as memory, and a system bus that couples various system components
including the memory to the computer processor. The system bus can
be of any of several types of bus structures including a memory bus
or memory controller, a peripheral bus, and a local bus using any
of a variety of bus architectures.
[0051] The computer typically includes one or more a variety of
computer-readable media accessible by the processor and including
both volatile and nonvolatile media and removable and non-removable
media. By way of example, computer-readable media can comprise
computer-storage media and communication media.
[0052] The computer storage media can store the software and data
in a non-transitory state and includes both volatile and
nonvolatile, removable and non-removable media implemented in any
method or technology for storage of software and data, such as
computer-readable instructions, data structures, program modules or
other data. Computer-storage media includes, but is not limited to,
RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM,
digital versatile disks (DVD) or other optical disk storage,
magnetic cassettes, magnetic tape, magnetic disk storage or other
magnetic storage devices, or any other medium that can be used to
store the desired information and that can be accessed and executed
by the processor.
[0053] The memory includes computer-storage media in the form of
volatile and/or nonvolatile memory such as read only memory (ROM)
and random access memory (RAM). A basic input/output system (BIOS),
containing the basic routines that help to transfer information
between elements within the computer, such as during start-up, is
typically stored in the ROM. The RAM typically contains data and/or
program modules that are immediately accessible to and/or presently
being operated on by the processor.
[0054] The computer may also include other removable/non-removable,
volatile/nonvolatile computer-storage media, such as (a) a hard
disk drive that reads from or writes to non-removable, nonvolatile
magnetic media; (b) a magnetic disk drive that reads from or writes
to a removable, nonvolatile magnetic disk; and (c) an optical disk
drive that reads from or writes to a removable, nonvolatile optical
disk such as a CD ROM or other optical medium. The computer-storage
medium can be coupled with the system bus by a communication
interface, wherein the interface can include, e.g., electrically
conductive wires and/or fiber-optic pathways for transmitting
digital or optical signals between components. Other
removable/non-removable, volatile/nonvolatile computer storage
media that can be used in the exemplary operating environment
include magnetic tape cassettes, flash memory cards, digital
versatile disks, digital video tape, solid state RAM, solid state
ROM, and the like.
[0055] The drives and their associated computer-storage media
provide storage of computer-readable instructions, data structures,
program modules and other data for the computer. For example, a
hard disk drive inside or external to the computer can store an
operating system, application programs, and program data.
[0056] Thus, the scope of the disclosed invention should be
determined by the appended claims and their legal equivalents,
rather than the examples given. In describing embodiments of the
invention, specific terminology is used for the sake of clarity.
For the purpose of description, specific terms are intended to at
least include technical and functional equivalents that operate in
a similar manner to accomplish a similar result. Additionally, in
some instances where a particular embodiment of the invention
includes a plurality of system elements or method steps, those
elements or steps may be replaced with a single element or step;
likewise, a single element or step may be replaced with a plurality
of elements or steps that serve the same purpose. Moreover, while
this invention has been shown and described with references to
particular embodiments thereof, those skilled in the art will
understand that various substitutions and alterations in form and
details may be made therein without departing from the scope of the
invention. Further still, other aspects, functions and advantages
are also within the scope of the invention; and all embodiments of
the invention need not necessarily achieve all of the advantages or
possess all of the characteristics described above. Additionally,
steps, elements and features discussed herein in connection with
one embodiment can likewise be used in conjunction with other
embodiments. Still further, the components, steps and features
identified in the Background section are integral to this
disclosure and can be used in conjunction with or substituted for
components and steps described elsewhere in the disclosure within
the scope of the invention. In method claims, where stages are
recited in a particular order--with or without sequenced prefacing
characters added for ease of reference--the stages are not to be
interpreted as being temporally limited to the order in which they
are recited unless otherwise specified or implied by the terms and
phrasing.
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